Blue Sea Systems - 2015 Catalog

TECH

tip

by BLUE SEA SYSTEMS

A T T E R Y

A N A G E M E N T

Battery Switches Explained

Purpose

Battery switches isolate the potentially destructive energy in the

battery banks when the boat is not in use or during emergencies.

ABYC E-11.6.1.2.1: A battery switch shall be installed in the

positive conductor(s) from each battery or battery bank with

a CCA rating greater than 800 amperes or 100 Ah if CCA

is unavailable.

Battery Switch Ratings

The UL standard for marine battery switches is UL 1107. This

standard rates switches for 5 minute and 1 hour time periods.

These ratings are not useful to the boater using a switch in the

engine starting circuit where current durations may be 10-60

seconds. For this reason, Blue Sea Systems uses additional

testing, consisting of a high amperage load during a cranking

period of 10 seconds. An additional 60-second rating,

representative of the load imposed on a battery switch in the

starting circuit under very difficult starting conditions, is also

provided. These 10 and 60 second ratings are in addition to the

testing done to UL 1107.

Selecting a Battery Switch

Based on Cranking Rating

• Known Engine Cranking Amperage:

Use the engine

manufacturer's recommended CCA rating to guide the

selection of an appropriate switch.

• Known Engine Size:

A general rule of thumb is 1 cranking

Ampere per cubic inch for gas engines and 2 cranking

Amperes per cubic inch for diesels.* This is generally

conservative for modern engines.

• Unknown Engine Size:

You can use the battery’s

Cold Cranking Amps (CCA) rating as an approximate guideline

when trying to select the appropriate size battery switch. Keep

in mind the battery must be appropriately sized for the engine

based on the engine manufacturer's recommendations.

Based on Continuous Rating

•

An electrical budget should be made to add up the maximum

continuous current capable of traveling through the switch. You

can then select the appropriate size switch based on its

continuous amperage rating.

*From Ed Sherman in Power Boater’s Guide to Electrical Systems

Switch Family

-Series

-Series HD-Series ML-RBS

Maximum

Battery CCA

800

1000

1500

Maximum

Approximate

Battery Size

4Dx2

BATTERY MANAGEMENT IS CENTRAL TO THE SAFE

OPERATION OF A BOAT OR VEHICLE

All boats and vehicles with an engine have at least one battery whose

primary purpose is starting the engine and providing power for loads

such as lights, pumps, and electronics. The safe switching between

batteries, loads, and charge sources is achieved using products in

this section:

1) Manual Battery Switches

2) Remote Battery Switches (RBS)

3) Automatic Charging Relays (ACR)

4) Low Voltage Disconnects (LVD)

Considerations When Choosing a Battery Switch

1. Requirement:

ABYC requires a battery switch on every boat

with a battery over 800 Cold Cranking Amps (CCA). This

requirement exists so the potentially destructive energy in the

batteries can be isolated in the event of a fire. A battery switch is

also used in many vehicle applications when high capacity storage

batteries are used for purposes other than starting an engine.

2. Proper Location:

The United States Coast Guard (USCG) and ABYC

recommends that a battery switch be mounted as close to the

battery as possible to reduce voltage drop and long runs of heavy

and expensive battery cables and in a location that can be easily

accessed in the event of a fire.

3. Proper Size:

Read the TECH Tip, “Selecting a Battery Switch”.

4. Battery Switch Functions:

A list of Manual Battery Switch

operational diagrams is on page 16.

Manual Battery Switches

are commonly used on small boats or

vehicles where the batteries are located near the operator, allowing

the high amperage switching and the control of the switch to be the

same location. On large boats or vehicles, battery switches may be

mounted close to the batteries to avoid long cable runs. This lack of

operator access can create a dangerous situation in the event of a

fire in the engine room when the battery switch must be turned off.

Remote Battery Switches (RBS)

are ideal when there is not an

easily accessible location near the batteries to mount the battery

switch, requiring either a long cable run or a battery switch mounted

in a difficult to access location. An introduction to Remote Battery

Switches is on page 25.

Low Voltage Disconnects (LVD)

sense low battery voltage and

disconnects non-critical loads to save power for engine starting.

A full description and specification of the M-LVD is on page 24.

Automatic Charging Relays (ACR)

automatically combine two battery

banks during charging and isolates batteries when discharging and

optionally when starting the engine. Read the TECH Tip explaining

how ACRs work on page 28. Use the ACR Selection Chart on page 29

to choose the right ACR for your application.